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144 lines
6.5 KiB
HTML
144 lines
6.5 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This manual is for GNU MPC, a library for multiple precision complex arithmetic,
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version 1.0.3 of February 2015.
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Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 INRIA
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with no
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Invariant Sections. A copy of the license is included in the section
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entitled "GNU Free Documentation License." -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Initializing Complex Numbers (GNU MPC 1.0.3)</title>
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<meta name="description" content="Initializing Complex Numbers (GNU MPC 1.0.3)">
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<meta name="keywords" content="Initializing Complex Numbers (GNU MPC 1.0.3)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="Complex-Functions.html#Complex-Functions" rel="up" title="Complex Functions">
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<link href="Assigning-Complex-Numbers.html#Assigning-Complex-Numbers" rel="next" title="Assigning Complex Numbers">
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<link href="Complex-Functions.html#Complex-Functions" rel="prev" title="Complex Functions">
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<style type="text/css">
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Initializing-Complex-Numbers"></a>
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<div class="header">
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<p>
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Next: <a href="Assigning-Complex-Numbers.html#Assigning-Complex-Numbers" accesskey="n" rel="next">Assigning Complex Numbers</a>, Up: <a href="Complex-Functions.html#Complex-Functions" accesskey="u" rel="up">Complex Functions</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Initialization-Functions"></a>
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<h3 class="section">5.1 Initialization Functions</h3>
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<p>An <code>mpc_t</code> object must be initialized before storing the first value in
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it. The functions <code>mpc_init2</code> and <code>mpc_init3</code>
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are used for that purpose.
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</p>
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<dl>
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<dt><a name="index-mpc_005finit2"></a>Function: <em>void</em> <strong>mpc_init2</strong> <em>(mpc_t <var>z</var>, mpfr_prec_t <var>prec</var>)</em></dt>
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<dd><p>Initialize <var>z</var> to precision <var>prec</var> bits
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and set its real and imaginary parts to NaN.
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Normally, a variable should be initialized once only
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or at least be cleared, using <code>mpc_clear</code>, between initializations.
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</p></dd></dl>
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<dl>
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<dt><a name="index-mpc_005finit3"></a>Function: <em>void</em> <strong>mpc_init3</strong> <em>(mpc_t <var>z</var>, mpfr_prec_t <var>prec_r</var>, mpfr_prec_t <var>prec_i</var>)</em></dt>
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<dd><p>Initialize <var>z</var> with the precision of its real part being
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<var>prec_r</var> bits and the precision of its imaginary part being
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<var>prec_i</var> bits, and set the real and imaginary parts to NaN.
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</p></dd></dl>
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<dl>
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<dt><a name="index-mpc_005fclear"></a>Function: <em>void</em> <strong>mpc_clear</strong> <em>(mpc_t <var>z</var>)</em></dt>
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<dd><p>Free the space occupied by <var>z</var>. Make sure to call this function for all
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<code>mpc_t</code> variables when you are done with them.
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</p></dd></dl>
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<p>Here is an example on how to initialize complex variables:
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</p><div class="example">
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<pre class="example">{
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mpc_t x, y;
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mpc_init2 (x, 256); /* precision <em>exactly</em> 256 bits */
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mpc_init3 (y, 100, 50); /* 100/50 bits for the real/imaginary part */
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…
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mpc_clear (x);
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mpc_clear (y);
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}
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</pre></div>
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<p>The following function is useful for changing the precision during a
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calculation. A typical use would be for adjusting the precision gradually in
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iterative algorithms like Newton-Raphson, making the computation precision
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closely match the actual accurate part of the numbers.
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</p>
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<dl>
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<dt><a name="index-mpc_005fset_005fprec"></a>Function: <em>void</em> <strong>mpc_set_prec</strong> <em>(mpc_t <var>x</var>, mpfr_prec_t <var>prec</var>)</em></dt>
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<dd><p>Reset the precision of <var>x</var> to be <strong>exactly</strong> <var>prec</var> bits,
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and set its real/imaginary parts to NaN.
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The previous value stored in <var>x</var> is lost. It is equivalent to
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a call to <code>mpc_clear(x)</code> followed by a call to
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<code>mpc_init2(x, prec)</code>, but more efficient as no allocation is done in
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case the current allocated space for the mantissa of <var>x</var> is sufficient.
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</p></dd></dl>
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<dl>
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<dt><a name="index-mpc_005fget_005fprec"></a>Function: <em>mpfr_prec_t</em> <strong>mpc_get_prec</strong> <em>(mpc_t <var>x</var>)</em></dt>
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<dd><p>If the real and imaginary part of <var>x</var> have the same precision, it is returned,
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otherwise, 0 is returned.
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</p></dd></dl>
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<dl>
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<dt><a name="index-mpc_005fget_005fprec2"></a>Function: <em>void</em> <strong>mpc_get_prec2</strong> <em>(mpfr_prec_t* <var>pr</var>, mpfr_prec_t* <var>pi</var>, mpc_t <var>x</var>)</em></dt>
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<dd><p>Returns the precision of the real part of <var>x</var> via <var>pr</var> and of its imaginary part
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via <var>pi</var>.
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</p></dd></dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Assigning-Complex-Numbers.html#Assigning-Complex-Numbers" accesskey="n" rel="next">Assigning Complex Numbers</a>, Up: <a href="Complex-Functions.html#Complex-Functions" accesskey="u" rel="up">Complex Functions</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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